1. Technical Field
The present invention relates to a transfer device, an image forming method and an image forming apparatus in an electrophotographic system.
2. Related Art
Proposed is an image forming apparatus with a transfer device that visualizes a latent image of an image carrier by developing it with a developing unit and transfers the toner image on the image carrier directly to a transfer material, such as paper. Furthermore, proposed is an image forming apparatus with a transfer device that visualizes a latent image of an image carrier by developing it with developing units, and then transfers the toner image on the image carrier onto an intermediary transfer medium, such as a drum or a belt stretched across a plurality of rollers, from whence the toner image on the intermediary transfer medium is transferred to a transfer material.
Disclosed in JP-A-3-4241 is an imaging unit that develops a latent image, which is on a photoreceptor functioning as an image carrier, into a toner image; and includes a transfer drum that transfers the toner image on the photoreceptor onto the transfer material. This transfer drum includes transfer material grip members for holding the transfer material, an adsorption electrostatic charger for electrostatically adsorbing the transfer material onto the transfer drum, a transfer electrostatic charger for transferring the toner image on the photoreceptor onto the transfer material, and a releasing electrostatic charger for releasing the transfer material, to which the toner image has been transferred from the transfer drum.
Disclosed in JP-T-2000-508280 is an image forming apparatus equipped with a transfer drum in which a latent image on a photoreceptor is developed with a liquid developer into a toner image; then, the toner image on the photoreceptor is transferred to an intermediary transfer drum that functions as an intermediary transfer medium; and the toner image on the intermediary transfer drum is transferred to a transfer material. The toner image on the intermediary transfer drum is transferred to the transfer material by applying heat and pressure. In addition, the transfer drum has transfer material grip members that grip the transfer material. It also has detach members on the outside of the transfer drum, which serves to release the transfer material from the transfer drum.
The image forming apparatus disclosed in JP-A-3-4241 requires a plurality of electrostatic chargers such as the adsorption electrostatic charger, the transfer electrostatic charger, and the releasing electrostatic charger within the transfer drum, making for a structurally complicated device as well as causing difficulties for controlling the positioning of the transfer material. In addition, because the image forming apparatus disclosed in JP-T-2000-508280 uses applied heat and pressure to transfer the toner image onto the transfer material, the adhesion between the transfer material, onto which the toner image has been transferred, and the transfer drum is increased, making it difficult to release the transfer material from the transfer drum as well as causing difficulties for positioning the transfer material.